Formation of conductive materials is an important fabrication process in integrated circuit (IC) production. Thin conductive films are used in creating any number of IC structures. Examples of these structures include, for example, interconnects, capacitor electrodes (e.g., metal-insulator-metal (MIM) electrodes), etc.
The requirements of a conductive material formation process can be demanding. In many cases, for example, conductive films need to be deposited at reasonably low temperatures tolerated by other materials used in integrated circuits. In addition, for example, the conductive films need to be high quality conformal films formed over a substrate surface, e.g., openings, deep trenches, container capacitor openings, etc. Furthermore, such films need to be formed with high throughput.
Various processes can be used to form such films. For example, physical processes (e.g., physical vapor deposition (PVD), evaporation, sputtering) or chemical processes (e.g., chemical vapor deposition (CVD) or plating) may be used. In addition, electroplating has been advantageously used in forming conductive and conformal films at high throughput.
In the electroplating process, a seed film can be initially applied to IC structures during processing. The seed film can then be used as a conductive surface on which the electroplating process can then take place. The seed films are typically formed by either the physical or chemical film forming process mentioned above. Typical processes for forming seed films used in electroplating conductive films, however, have various disadvantages. For example, seed films produced by either CVD or PVD in many circumstances require an overabundance of seed film to be deposited to ensure film continuity. The result of this overabundance is that certain areas of the seed film have thicker deposits as compared to other areas. This is especially true for high aspect ratio structures, such as openings or trenches (e.g., container capacitor openings), which typically require a thick deposit in order to yield sufficient seed layer on the side of the walls of the structure for successful plating therein. Further, for example, adhesion of an electroplated layer to seed films deposited by PVD may only be marginal.
In a specific example, electroplated platinum is an attractive candidate for a bottom MIM electrode because of the high quality conformal films that can be deposited at high throughput. The typical PVD platinum seed layer, however, could be improved since it requires a thick deposit in order to yield sufficient platinum on the sidewalls of the container for successful plating. Also, adhesion is only marginal with the PVD platinum seed layer.
Thus, a need exists for creating uniform seed films for use in the electroplating process.